As output power generated by a fuel cell at the time of driving in the state where a vehicle is degraded (aged) is decreased, power performance is decreased. In particular, a vehicle is momentarily accelerated when entering a highway, and thus has a trouble in adjusting to a speed flow of other vehicles, such that driver's safety may be at risk.
The fuel cell vehicle hybridizes a fuel cell as a main power source and a high voltage battery as a secondary power source to improve fuel efficiency and power performance. For the development of the fuel cell vehicle, the optimum power distribution is performed before the fuel cell ages. Therefore, if the fuel cell is degraded and thus aged, the fuel cell is out of the optimum power distribution.
In order to maintain the optimum power distribution, a technique for estimating the degradation in the fuel cell is indispensable. In the case of reversible degradation, the difference in relative humidity between atmospheric temperature at a low temperature region and atmospheric temperature at a high temperature region is great, and a water content in the fuel cell greatly varies depending on a driving history. In particular, the difference in performance greatly varies depending on whether generated water due to a reaction of hydrogen and oxygen is discharged in the air or whether the generated water is contained in the fuel cell. The performance of the fuel cell is degraded regardless of the excessive water content or the insufficient water content in the fuel cell, and the performance of the fuel cell is best when the relative humidity is maintained at 100%. A water content estimator is required to prevent the performance degradation depending on the water content in the fuel cell.
The degradation measurement method needs to measure the degradation in real time in order to be applied to a real vehicle, but a sensor capable of measuring the irreversible degradation is not present. To estimate the reversible degradation, a relative humidity sensor needs to be equipped in the vehicle. In this case, however, costs may be increased due to the relative humidity sensor. Therefore, there is a need to develop the estimator that may estimate the reversible degradation and the irreversible degradation of the fuel cell in real time in the vehicle.
The matters described as the related art have been provided only for assisting in the understanding for the background of the present invention and should not be considered as corresponding to the related art known to those skilled in the art.